Controlling foam in submerged and aerated propagation of microorganisms



AT'EORN EYS Filed June 3, 1949 W. O. GORDON ETAL CONTROLLING FOAM IN SUBMERGED AND AERATED PROPAGATION OF MICROORGANISMS April 14, 1953 Patented Apr. 14, 1953 CONTROLLING FOAM IN SUBMERGED AND AERATED PROPAGATION F MICROOR- GANISMS Willis 0. Gordon, New Orleans, La., and Matthew K. Veldhuis, Winter Haven, Fla., assignors to the United States of America as represented by the Secretary of Agriculture Application June 3, 1949, Serial No. 97,065

4 Claims. (01. 195-94).

(Granted under Title 35, U. s. Code (1952),

sec. 266) This application is made under the act of March 3, 1883, .asamended by the act of April 30, 1928, and the invention herein described, if patented in any country, maybe manufactured and used byor for the Government of, the United States of America for governmental purposes throughout the world without the payment to us of any royaltythereon,

This invention relates to the propagation of micro-organisms',"such as'yeast, in which the organism is propagated by culturing it submerged in a liquid nutrient medium, and air. is continuously mixed with the medium to furnish the required oxygen. Atcrtairl stages during the growth of the organism, themedium tends-to form" a foam which-is 'quite stable, resulting in considerable trouble, and loss 'Of the organism and medium by ejection of ,foam from the usual typepropagator through the airvent. In prior art processes; "antifo'a'ming "(agents havev been added'to the'nutr'ient medium to inhibit the foaming, but this is expensive and bothersome. This invention has among its objects a simple and eificient apparatus. for controlling such foaming.

For a detail description of the invention, reference is made to the accompanying drawing, which schematically shows in a single figure the essential features of an apparatus according to the invention.

In the drawing, a plurality of corresponding propagator tanks ll, 12 and I3 for containing liquid medium are arranged in series. Any number, from one single propagator tank up to three, will generally suffice. The liquid nutrient medium continuously feeds into propagator tank ll through inlet pipe l1, feeds continuously through such propagator tank, and feeds to propagator tank I2 through medium pipe [8, then to propagator tank [3 through medium pipe [3, and finally through medium pipe 20 to receiver tank 2|, the time of passage and degree of organism propagation depending on the rate of feeding the nutrient medium and size of the propagators. Pipe I8 is connected to tank H at a point below its connection to second tank l2, and pipes I9 and 20 are similarly connected to tanks 12 and I3, and to tanks l3 and 2|, respectively. Pipes I8, l9 and 20 are so arranged that the medium feeds through them by overflow.

Air is continuously forced through air pipe 22, through branches 23, 24 and 25, and is introduced into the medium in the several propagator tanks through porous tubes 26, 21 and 28 at a rate suflicient to keep the medium well stirred and well aerated, excess air and formed gases being vented from the propagators through vents 36, 3| and 32, if these vents are open.

As foam is formed in the propagator tanks, it rises on the surface of the medium and passes with an air stream at substantial velocity from propagator tank ll to propagator tank 12 through a relatively large foam pipe 35, then to propagator tank |3 through foam pipe 36 and, if any is yet present, finally to receiver tank 2| through foam pipe 31, these foam pipes establishing communication between their respective tanks near the foam strikes the targets and is disintegrated,

andthe resulting small amount of liquid drains into the liquid medium. 5

"Medium pipes l8, l9 and 20 are provided with cut-off valves 40, 4| and 42, respectively, and it is possible to close these valves in operation of the apparatus so that the liquid medium also flows from the several propagators through foam pipes 35, 36 and 31. This increases the capacity of the apparatus due to the liquid level standing higher in each propagator than if pipes [3, I9 and 20 are used, and gives satisfactory operation if the amount of foaming is not too large.

Cut-off valves 45, 46 and 4'! are also provided in pipes 35, 36 and 31, so that with ClOSlIlg of the proper valves any propagator may be isolated for cleaning purposes, etc.

In operation vents 30, 3| and 32 maybe closed and the excess air and gases vented through pipes 35, 36 and 31. This is desirable if contamination through the vents is probable.

The successful operation of the apparatus in the propagation and production of micro-organisms such as yeast depends in part upon the impingement of the stream emerging from the foam pipe against the target at a velocity which will disintegrate the foam. This is accomplished by employing a foam pipe of cross sectional area such that the velocity of gas and foam passing therethrough is substantially greater than the velocity rising through the propagator. To this end the foam pipe should have a cross sectional area of from A; to /3 that of the propagator tank. When employing propagator tanks of about three feet in diameter, foam pipes of from six inches to one foot in diameter may be employed to achieve highly satisfactory results. Employing an aeration rate of about cubic feet per minute results in approximately 500 feet specific form of the target may be varied con-. siderably. For example, it may be a screerna series of perforated baffles or screens and the like of flat or curved contour. that the impingement surfaces ofthe target be perforated or otherwise foraminous in order to.

achieve the most efficient foam disintegration.

Having thus described the invention, what is claimed isg' 11A continuous process of propagating microorganisms comprising culturing them in a liquid nut "entlmedium contained in a propagator tank, continuously feeding liquid medium therein con tin usly introducing air into the medium for aera on thereof, continuously passingproduced foam and introdueedair from the upper portion offthepropagator tank to the upper portion of asecondftankjthrough' a foam pipe communicatingl'w ithl'the tanks to disintegrate the foam, and continuously feeding the liquid medium fromthe propagator. tank to the second tank through a mediumlpipe, thaliquid level in thetanks being maintained lowerthanthepoints of communication of. the foampipe therewith.

'2; The process of claim'l characterized in that the foam strikes against a perforated plate placed adjacent theioiztlet of the foam pipe to aid in disintegrating the foam.

3,.Anapparatus for thecontinuous propaga- It is important tio nof micro-organismsby culturing them in an aerated, liquidnutrient: medium,. comprising a propagator tank for containing the medium, said tank having means for continuously feeding liquid medium therein and means for continuously introducing air into the medium for aeration thereof, and a second tank arranged in series with the propagator tank, the tanks communicating through a foam, pipe connected to their upper portions, so that introduced air and foam formed in: the propagator tank pass therefrom through the foam pipe into the second tank and the foam is, thereby; disintegrated, the propagator tank communicating with the second tank through a mediumpipe connected to the tanks at points belowthepointsof connection of the foam pipe to .the tanks so that the liquid medium continuously feeds by overflow from the propagator tankthrough the medium pipeto the second tank, and the liquidv level in" th'e tanks is. maintained lower than the connections of-the foamp pe thereto.

4'. The apparatus of v claim .3 characterized-in thata perforatedplate is placed adjacentthe; outlet of the foamwpipe .againstwhich .the. foam trikes thus to aid in its disintegration.

WILLIS 0.; GORDON.

References Cited; in. the. file-of this patent UNITED STATES PATENTS 

1. A CONTINUOUS PROCESS OF PROPAGATING MICROORGANISMS COMPRISING CULTURING THEM IN A LIQUID NUTRIENT MEDIUM CONTAINED IN A PROPAGATOR TANK, CONTINUOUSLY FEEDING LIQUID MEDIUM THEREIN, CONTINUOUSLY INTRODUCING AIR INTO THE MEDIUM FOR AERATION THEREOF, CONTINUOUSLY PASSING PRODUCED FOAM AND INTRODUCED AIR FROM THE UPPER PORTION OF THE PROPAGATOR TANK TO THE UPPER PORTION OF A SECOND TANK THROUGH A FOAM PIPE COMMUNICATING WITH THE TANKS TO DISINTEGRATE THE FOAM, AND CONTINUOUSLY FEEDING THE LIQUID MEDIUM FROM THE PROPAGATOR TANK TO THE SECOND TANK THROUGH A MEDIUM PIPE, THE LIQUID LEVEL IN THE TANKS BEING MAINTAINED LOWER THAN THE POINTS OF COMMUNICATION OF THE FOAM PIPE THEREWITH.
 3. AN APPARATUS FOR THE CONTINUOUS PROPAGATION OF MICRO-ORGANISMS BY CULTURING THEM IN AN AERATED, LIQUID NUTRIENT MEDIUM, COMPRISING A PROPAGATOR TANK FOR CONTAINING THE MEDIUM, SAID TANK HAVING MEANS FOR CONTINUOUSLY FEEDING LIQUID MEDIUM THEREIN AND MEANS FOR CONTINUOUSLY INTRODUCING AIR INTO THE MEDIUM FOR AERATION THEREOF, AND A SECOND TANK ARRANGED IN SERIES WITH THE PROPAGATOR TANK, THE TANKS COMMUNICATING THROUGH A FOAM PIPE CONNECTED TO THEIR UPPER PORTIONS, SO THAT INTRODUCED AIR AND FOAM FORMED IN THE PROPAGATOR TANK PASS THEREFROM THROUGH THE FOAM PIPE INTO THE SECOND TANK AND THE FOAM IS THEREBY DISINTEGRATED, THE PROPAGATOR TANK COMMUNICATING WITH THE SECOND TANK THROUGH A MEDIUM PIPE CONNECTED TO THE TANKS AT POINTS BELOW THE POINTS OF CONNECTION OF THE FOAM PIPE TO THE TANKS SO THAT THE LIQUID MEDIUM CONTINUOUSLY FEEDS BY OVERFLOW FROM THE PROPAGATOR TANK THROUGH THE MEDIUM PIPE TO THE SECOND TANK, AND THE LIQUID LEVEL IN THE TANKS IS MAINTAINED LOWER THAN THE CONNECTIONS OF THE FOAM PIPE THERETO. 